WLAN Downlink Timing Alignment for Non-STR STA Reception
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Solution Overview
Problem
In multi-channel WLAN operations, non-STR STAs face reception failures due to overlapping acknowledgement responses in the uplink with ongoing downlink data transmissions on another channel, leading to inefficient throughput and reliability.
Innovation Solution
The AP aligns the endings of simultaneous downlink data transmissions on multiple channels to prevent overlap with uplink acknowledgements, ensuring that non-STR STAs can receive data without interference, by dynamically adjusting transmission timing based on the STR capability and reception capability of the STA.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If simultaneous downlink transmissions are provided to non-STR STA on multiple channels, then throughput is improved, but reception failure occurs due to overlap between uplink acknowledgements and downlink data transmissions
Solution Approach 1:
The AP determines whether the STA is STR-capable before initiating simultaneous downlink transmissions. This preliminary classification allows the AP to pre-plan transmission strategies: for non-STR STAs, the AP avoids overlapping transmissions that would cause reception failures, while for STR-capable STAs, the AP can fully utilize multi-channel simultaneous transmissions to maximize throughput.
Solution Approach 2:
The system dynamically adjusts downlink transmission timing based on the STA's STR capability. For non-STR STAs, the AP coordinates transmission timings to prevent overlap between uplink acknowledgements and downlink data. This dynamic timing adjustment enables the system to adapt transmission behavior to individual STA capabilities, resolving the contradiction between throughput improvement and reception reliability.
2Productivity
If multi-channel operation is implemented, then bandwidth is increased and throughput is improved, but timing coordination complexity increases due to asynchronous medium access on each channel
Solution Approach 1:
The invention changes the timing parameter of downlink transmissions based on the STA's STR capability. By adjusting transmission start times and durations, the system maintains simple asynchronous medium access on each channel while ensuring that acknowledgements and data transmissions do not overlap for non-STR STAs. This parameter adjustment resolves the complexity issue without sacrificing throughput benefits.
3Loss of time
If downlink transmissions begin at different times on multiple channels, then latency is reduced by utilizing first available channel, but overlap with uplink acknowledgements causes reception failure
Solution Approach 1:
The AP performs preliminary timing coordination by determining the duration of downlink transmissions and comparing it with the expected acknowledgement timing. This preliminary action allows the AP to schedule transmissions that minimize overlap risks while still utilizing multiple channels efficiently, thus reducing latency without sacrificing reception reliability.
Solution Approach 2:
The system uses feedback from the STA's STR capability indication to adjust transmission timing. The AP incorporates this feedback into its scheduling decisions, ensuring that for non-STR STAs, the timing of downlink transmissions is coordinated with expected acknowledgement times, preventing reception failures while maintaining low latency through multi-channel operation.
Data Source
Figure 1~2A
Figure 2B~2C
Figure 3
AI summary
Methods and a devices are provided is for receiving simultaneous downlink transmissions at a mobile station (STA). Information regarding whether endings of simultaneous data transmissions to the mobile station are to be aligned is transmitted to an access point (AP). The simultaneous data transmissions are between the AP and the STA over a pair of channels. Reception begins of a first data transmission, from the AP, on a first channel of the pair of channels. Reception begins of a second data transmission, from the AP, on a second channel of the pair of channels. The second data transmission overlaps at least a portion of the first data transmission. Reception of the second data transmission ends upon an end of the first data transmission when the information indicates that the endings of simultaneous downlink data transmissions are to be aligned.